Flexible porous web having a permanent humidity sensor for indicating release of material therefrom

Abstract

A porous web having a permanent humidity detecting sensor is disclosed in which a metal salt is permanently bonded in the porous web matrix. The metal salt undergoes a color change from its hydrated to its dehydrated state to detect a change in humidity of a surrounding environment. Nonwoven fibrous webs having a permanent humidity detecting sensor are especially adapted for containing materials such as fabric softeners that may be released upon the conditions of a conventional clothes dryer for treatment of the clothes and visual detection of the release of softener by color change of the humidity sensor.

What is claimed is: 
     
       1. A porous web having a permanent humidity detecting sensor comprising a porous web having a substantially porous matrix and having bonded therein a metallic salt that undergoes a color change from its hydrated to its dehydrated state, said metallic salt bonded in said matrix with a polymeric binder that permanently bonds the salt in said matrix and allows the salt to undergo a visible color change upon a change in humidity of the environment to which it is exposed, said porous matrix containing an agent for release from the matrix, said release detected by a visual observation of said color change.   
     
     
       2. The device of claim 1 wherein said web is a nonwoven fibrous substrate formed from staple fibers wherein said polymeric binder binds said metallic salt and the fibers in the interstices of the porous matrix to substantially maintain the web porosity. 
     
     
       3. The device of claim 2 wherein said polymeric binder and metal salt are derived from an aqueous mixture of a polymeric emulsion containing the metallic salt. 
     
     
       4. The device of claim 3 wherein said polymeric emulsion is selected from the group consisting of acrylic and polyvinyl acetate emulsions, and mixtures thereof, and said metal salt is a soluble salt of cobalt. 
     
     
       5. The device of claim 4 wherein the cobalt salt is cobaltous chloride. 
     
     
       6. The device of claim 1 wherein said porous matrix has a void volume of about 40 to about 90%. 
     
     
       7. The device of claim 1 wherein said agent is a solid fabric softener that is released by melting at the drying temperatures of a conventional dryer. 
     
     
       8. The device of claim 7 wherein said fabric softener is uniformly contained in said matrix. 
     
     
       9. A porous web having a permanent humidity detecting sensor comprising a nonwoven porous web of staple fibers having a substantially porous matrix and having bonded therein a metallic salt that undergoes a color change from its hydrated to its dehydrated state, said porous matrix having a void volume of about 40 to about 90%, said metallic salt bonded in said matrix with a polymeric binder that permanently bonds the fibers and the salt in said matrix and allows the salt to undergo a visible color change upon a change in humidity of the environment to which it is exposed, said porous matrix containing an agent for release from the matrix, said release detected by a visual observation of said color change, said polymeric binder and metal salt are derived from an aqueous mixture of a polymeric emulsion containing the metallic salt.   
     
     
       10. The device of claim 9 wherein said agent is a solid fabric softener that is released by melting at the drying temperatures of a conventional dryer.